1. Field of the Invention
The present invention relates to the methods for detection of vapors, and particularly to the fluorescence-based method of detection employing solid films of sensory porphyrins in the aggregated form. In one preferred embodiment, the aggregation of porphyrin molecules leads to initial depression of chromophore emission due to self-quenching effect. The binding of analyte molecules to porphyrin sensitive layer forms porphyrin-analyte complexes, which destroy initial aggregate structure and induce the strong fluorescence enhancement. Aggregate-sensing films usually provide higher and faster response than porphyrins isolated in a polymer matrix. Such effect is new and its application can considerably improve the sensor performance. In another preferred embodiment, the sensitive material is incorporated into an optical fiber system enabling efficient excitation of the dye and collecting the fluorescent signal form the sensitive material on the remote end of the system.
The method can be used in all applications where highly sensitive detection of volatile organic compounds, such as vapors of benzene, alcohol, chloroform, dimethyl methylphosphonate (DMMP) that is a simulant of Sarin, Soman and other chemical warfare agents, is required for environmental monitoring, chemical industry and medicine.
2. Background of the Invention
Today, there is a high demand for chemical sensor for detecting low concentration levels of analytes present in the liquid and gaseous phase. Selectivity to target molecules is also highly desired. Traditional methods of quantitative detection of analytes based on gas chromatography and mass spectrometry require complex laboratory equipment. Among modern approaches for real time monitoring of gaseous analytes, mainly three kinds of sensing elements have been investigated: microelectrodes, quartz crystal microbalance and surface acoustic wave devices. Generally all these methods are based on detection of only one parameterxe2x80x94signal intensity. Therefore reliable analyte identification requires significant increasing the number of individual sensors in the detector array.
Meanwhile, optical chemosensors, especially fluorescence-based chemosensors can provide many kinds of complex information, including changes in intensity, wavelengths and spectral shape, fluorescence lifetime. Hence such promising approach allowing detection of many parameters simultaneously should make possible the fabrication of highly sensitive, robust, multi-analyte-detecting arrays with fewer independent sensors. Moreover, the possibility of remote sensing using optical fluorescence technique offers many serious advantages over other traditional methods of real-time monitoring of toxic gases and pollutants.
Usually for luminescence sensing the porphyrins are immobilized in the neutral polymer films, sol-gel matrixes or membranes. The main idea of the matrix isolation is the prevention of porphyrin aggregation leading to the strong fluorescence selfquenching. Nothing has been reported yet about the design of fluorescence chemosensors based on thin films of aggregated porphyrins employing the fluorescence enhancement under gas exposure.
The present invention suggests new approach to the highly sensitive and selective detection of organic vapors using fluorescence properties of aggregated porphyrins. It is based on recently demonstrated new effect of strong enhancement of the fluorescence emission in the presence of molecules of organic vapors. In one preferred embodiment the fluorescent sensitive material is incorporated into a fiber-optical system allowing remote monitoring of large contaminated area.
The method can be used in all applications where highly sensitive detection of volatile organic compounds, such as vapors of benzene, alcohol, chloroform, dimethyl methylphosphonate (DMMP) that is a simulant of Sarin, Soman and other chemical warfare agents, is required for environmental monitoring, chemical industry and medicine.
It is an object of the present invention to improve performance of chemical sensors of organic vapors by employing the effect of fluorescence change of the thin films of aggregated porphyrins in the presence of target molecules.
Another object of the invention is to provide a simple and efficient method of detection of the fluorescence signal by measuring enhancement of the fluorescence in the presence of target vapors.
A further object is to provide a selection of efficient sensitive fluorescent material comprising a film of Tetraphenylporphyrin (TPP) and metaloporphyrin Zn-Tetraphenylporphyrin (Zn-TPP) aggregates.
Another object is to provide efficient method of processing the fluorescent signal from the sensitive material.
Still another object is to provide a possibility of remote monitoring of large contaminated area by incorporating the sensitive fluorescent material into an optical fiber system.
An additional object of the invention is to provide a method for fabrication of the fiber-optic fluorescence sensors achieving efficient excitation of the sensitive material and efficient collecting the fluorescence signal.
Briefly stated, the present invention provides a method of detection of different volatile organic compounds such as, vapors of benzene, alcohol, chloroform, dimethyl methylphosphonate (DMMP) that is a simulant of Sarin, Soman and other chemical warfare agents. The method employs the effect of strong fluorescence change in the thin films of aggregated porphyrins in the presence of target vapors.
The aggregation of porphyrin molecules leads to initial depression of chromophore emission due to self-quenching effect. The binding of analyte molecules to porphyrin sensitive layer forms porphyrin-analyte complexes, which destroy initial aggregate structure. That results in strong enhancement of the dye florescence quantum yield, appearance of new bands and shift of the dye fluorescent spectrum in the direction of shorter wavelengths. The method can be used in fluorescence chemical sensors of organic vapors for different applications including environmental monitoring, control of industrial processes and medicine.
The above, and other objects, features and advantages of the present invitation will become apparent from the following description read in conjunction with the accompanying drawings.